inv_admin_pages 
+-----+-------+--------------------------+
| PID | Title | File                     |
+-----+-------+--------------------------+
| 1   | Login | includes/pages/login.php | 
+-----+-------+--------------------------+
| 2   | Home  | includes/pages/home.php  | 
+-----+-------+--------------------------+
| 3   | Users | includes/pages/users.php | 
+-----+-------+--------------------------+

inv_admin_masks - every page,subsection BitWise Mask PID refers to the inv_admin_pages
+----+---------+-----+--------+
| ID | Bitwise | PID | OP     |
+----+---------+-----+--------+
| 1  | 1       | 1   |        | No SubSection ( OP ) will Show the Login Form
+----+---------+-----+--------+
| 2  | 2       | 1   | Login  | SubSection called Login will Log the user in
+----+---------+-----+--------+
| 3  | 4       | 1   | Logout | SubSection of Logout will Log the user out - Subsections still use the page ( login.php )
+----+---------+-----+--------+
| 4  | 1       | 2   |        | No Subsection Needed - Admin Home page just shows Stats/Admin Notes etc
+----+---------+-----+--------+
| 5  | 1      | 3   | View   | SubSection of View will list the current users
+----+---------+-----+--------+
| 6  | 2      | 3   | Edit   | SubSection of Edit - URL will look like index.php?pid=3&op=edit&id=1 - This means it will show details for that User
+----+---------+-----+--------+
| 7  | 4      | 3   | Delete | SubSection of Delete - URL: index.php?pid=3&op=delete&id=1 - Means it will delete user 1
+----+---------+-----+--------+
| 8  | 8     | 3   | Add    | SubSection of Add will allow the Admin/User to Add another user
+----+---------+-----+--------+

inv_users

+----+----------+
| ID | Username |
+----+----------+
| 1  | Test     |
+----+----------+
| 2  | Fred     |
+----+----------+

+----+----------+-------+
| ID | PID      | Mask  |
+----+----------+-------+
| 1  | 1        | 7     | 
+----+----------+-------+
| 2  | 1        | 7     | 
+----+----------+-------+
| 2  | 2        | 1     | 
+----+----------+-------+
| 2  | 3        | 15    | 
+----+----------+-------+